ABC News published a transcript of the message, which was found written on the inside of a boat where Tsarnaev hid from police.

It reads:

“The U.S. government is killing our innocent civilians, but most of you already know that… I can’t stand to see such [bullet hole] go unpunished. We Muslims are one body. You kill one of us, you hurt [bullet hole] us all.”

Tsarnaev has pleaded not guilty to a 30-count federal indictment stemming from explosions at the Boston Marathon's finish line last year that killed three people and injured 260. State officials and local law enforcement confirmed the authenticity of the image.

“His life story, the influences on him,” Peter H. White, a Washington, D.C., attorney, said in a Boston Herald interview about Tsarnaev's defense this week. “I think it’s all they have at this point. The evidence the government has appears very strong... I don’t think it’s an irrational choice at all. In some ways, it’s pretty obvious.”